1. Field of the Invention
The present invention relates to stepper, and more particularly to a stepper that includes two endless straps respectively mounted on to two swing arms of the stepper.
2. Description of Related Art
A conventional stepper in accordance with the prior art shown in FIG. 5 comprises a main frame (61) including a base (611) adapted to abut a supporting surface, two stands (612) respectively upwardly extending from two opposite sides of a front portion of the base (611) and a hand post (613) mounted on a free end of each of the two stands (612). Two swing arms (62) are pivotally mounted to a rear portion of the base (611). The two swing arms (62) are parallel to each other and swung opposite to each other. Each swing arm (62) has a rear end pivotally mounted to the rear portion of the base (611) and a front end having an air spring (63) mounted thereon. The air spring (63) has a first end pivotally connected to the front end of a corresponding one of the two swing arms (62) and a second end pivotally mounted to an inner side of a corresponding one of the two stands (612). Each swing arm (62) has an endless strap (621) movably sleeved thereon for user to step on the swing arms (62). A motor (64) is mounted to a rear end of the base (611) for driving the two endless straps (621). 
The two air springs (63) are provided to respectively provide a restitution force to two swing arms (62) after being downward stepped. However, each air spring (63) only mounted to one side of each of the two swing arms (62) so that the load of each of the two swing arms (62) is not average. Furthermore, the motor (64) is mounted to the rear portion of the base (611) so that the total length of the stepper is elongated.
For solving the above problem, the motor (64) is mounted under the two swing arms (62) and each side of each of the two swing arms (62) has at least one air spring (65) mounted on each of the two swing arms (62). As a result, the stepper should have at least four air springs for balancing the load from the two swing arms (62). Consequently, the manufacturing cost is raised.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional steppers.